The present invention relates generally to the delivery of a beneficial agent to a patient or into a system for later delivery to a patient. More specifically, the present invention relates to a sheath for covering a blunt end of a cannula.
Pointed cannulas, for use with injection sites, have been known for use in the medical arena. Such cannulas can be utilized to access a medicament contained within a container or to create a fluid flow path within a housing. An example of an injection site usable with a piercing cannula is disclosed in U.S. Pat. No. 4,412,573.
Within a housing, to create a fluid flow path, a pointed cannula is utilized that is forced through a septum to create a flow path within the housing. Injection sites, however, which are utilized on a repetitive basis can be damaged by repetitive piercing by a sharp cannula. This damage, known as coring or laceration, can result in a subsequent leakage within the housing.
Furthermore, the use of a pointed cannula has the further disadvantage that it can detrimentally affect the personnel using the pointed cannulas. For example, recently there has been much concern over the transfer of infectious agents and disease states, for example, acquired immune deficiency syndrome, by personnel piercing themselves with pointed cannulas. Further, many medications that are utilized can be dangerous if one is repeatedly exposed to such medicine by being pierced by the pointed cannula, e.g., chemotherapy drugs.
Accordingly, recently, blunt cannulas have been developed for utilization with specific injection sites that are designed to receive such cannulas. An example of such a site is set forth in U.S. Pat. No. 4,197,848. That patent discloses an injection site having a relatively low pressure device having a relatively thin, molded sealing member. The sealing member has an opening therethrough. The blunt cannula can be forced through the sealing member placing the cannula into fluid flow communication with a fluid flow pathway in the injection site.
Blunt cannulas have the advantage that the blunt end of the cannula cannot accidentally pierce the skin of the medical personnel. Accordingly, even if one accidentally contacts the cannula, the cannula will not pierce his skin.
For use with blunt cannulas, preslit injection sites have been developed. An example of these preslit injection sites includes U.S. patent application Ser. No. 07/147,414, assigned to the assignee of the instant patent application. The preslit injection site allows the blunt end of the cannula to be received within the injection site, establishing fluid communication.
For many applications, drugs may be mixed with a diluent before being delivered, for example, intravenously, to a patient. The diluent may be, for example, a dextrose solution, a saline solution, or even water. To this end, many such drugs are supplied in powder form and packaged in glass vials or ampules. Other drugs, such as some chemotherapy drugs, are packaged in glass vials or ampules in a liquid state.
Powder drugs may be reconstituted by utilizing a syringe to inject liquid into a vial for mixing; the syringe eventually withdrawing the mixed solution from the vial. When a drug must be diluted before delivery to a patient, the drug is often injected into a container of diluent after it is reconstituted; the container can be connected to an administration set for delivery to the patient.
There are a variety of examples of drug delivery systems. An example of such a system is disclosed in U.S. Pat. No. 4,850,978. The system includes a cartridge for introducing a beneficial agent into a fluid conduit for delivery of the agent to a patient. The cartridge includes a rigid hollow tube and an agent-containing chamber slidably mounted at least partially within the hollow tube. In a first, pre-use position, the chamber extends farther from the hollow tube than it does in a second position. A cannula is mounted to the hollow tube extending opposite the chamber. When the chamber is in the second position, the cannula pierces the closure means creating a fluid flow path.
U.S. Pat. No. 4,804,366 also discloses a drug delivery system including an adapter having an improved flow path means providing both an inlet and an outlet to the agent-containing chamber of a cartridge. The cartridge and adapter permit a single opening through the injection sites at opposite ends of the flow path means, while still permitting simultaneous flow both into and out of the chamber. An adapter and a cartridge is provided, including a rigid cannula with an inlet and an outlet and a shell substantially coaxial with and spaced from the cannula intermediate of the cannula inlet and the cannula outlet, so that the shell of the cannula define a channel therebetween. Both the cannula inlet and the cannula outlet are adaptable to form a single piercing opening in a resilient injection site associated with the receptacle of the delivery system. Both the channel outlet and cannula inlet are adapted to form a single piercing opening in a resilient injection site associated with the cartridge.
It is known to provide a removable cover for surrounding a first end of the cannula that is coupled to a set. The cover is removed prior to connecting the system to an injection site of a set. Typically, the cover is removed after the cannula inlet has pierced the cartridge chamber. Because the cover must be removed prior to connecting the system to a set, and typically, after the cannula inlet has pierced the cartridge chamber, there may be concerns vis-a-vis sterility and leakage of product through the outlet end of the cannula as well as the channel inlet.